Researchers from the University of Minnesota College of Science and Engineering have created graphene-based tiny electronic “tweezers” that can grab biomolecules floating in water with extraordinary efficiency. This, according to the team, could lead to a revolutionary handheld disease diagnostic system that could be run on a smartphone.

The graphene tweezers are said to be vastly more effective at trapping particles compared to other techniques used in the past due to graphene's extremely thin nature. The physical principle of tweezing or trapping nanometer-scale objects, known as dielectrophoresis, has been known for a long time and is typically practiced by using a pair of metal electrodes. From the viewpoint of grabbing molecules, however, metal electrodes are very blunt. They simply lack the “sharpness” to pick up and control nanometer-scale objects.

“Graphene is the thinnest material ever discovered, and it is this property that allows us to make these tweezers so efficient. No other material can come close,” said the research team leader. “To build efficient electronic tweezers to grab biomolecules, basically we need to create miniaturized lightning rods and concentrate huge amount of electrical flux on the sharp tip. The edges of graphene are the sharpest lightning rods.”

The team also showed that the graphene tweezers could be used for a wide range of physical and biological applications by trapping semiconductor nanocrystals, nanodiamond particles, and even DNA molecules. Normally this type of trapping would require high voltages, restricting it to a laboratory environment, but graphene tweezers can trap small DNA molecules at around 1 Volt, meaning that this could work on portable devices such as mobile phones.

The team made the graphene tweezers by creating a sandwich structure where a thin insulating material call hafnium dioxide is sandwiched between a metal electrode on one side and graphene on the other. Hafnium dioxide is a material that is commonly used in today’s advanced microchips. “One of the great things about graphene is it is compatible with standard processing tools in the semiconductor industry, which will make it much easier to commercialize these devices in the future,” said the team.

Another exciting aspect of this technology, that separates graphene tweezers from metal-based devices, is that graphene can also “feel” the trapped biomolecules. In other words, the tweezers can be used as biosensors with extreme sensitivity that can be displayed using simple electronic techniques.